delta rpms - can we turn them off

[Ville Skyttä]

On Wed, Jul 2, 2014 at 6:04 PM, Reindl Harald <h.reindl at thelounge.net> wrote:

> but it's just dangerous to assume that will be forever true

Agreed with this, but:

> and as you can see below with gzip you have *always*
> different results for the same data

This is not true, see below.

> [harry at srv-rhsoft:~/Desktop]$ tar -p -czf 1.tar.gz test.bin
> [harry at srv-rhsoft:~/Desktop]$ tar -p -czf 2.tar.gz test.bin
> [harry at srv-rhsoft:~/Desktop]$ tar -p -czf 3.tar.gz test.bin
> [harry at srv-rhsoft:~/Desktop]$ tar -p -czf 4.tar.gz test.bin
> [harry at srv-rhsoft:~/Desktop]$ tar -p -czf 5.tar.gz test.bin
> [harry at srv-rhsoft:~/Desktop]$ md5sum *.gz
> 8f132cafffe6d7a613a480a5e593abc8  1.tar.gz
> 3cf402bbbde27db631a2896af9365275  2.tar.gz
> 5cb1fc9f6628a41d71572862ea4c19a1  3.tar.gz
> bd51a4779ca4e2e9377488dc64ccaf1c  4.tar.gz
> 5506a0cfbf39cb28b05babba6755049a  5.tar.gz

These tests are faulty, they're not testing gzip with the same data.
You're (well tar is internally) gzipping five temporary tarballs that
have different timestamps and/or filenames, and gzip's default
behavior is to store original file's filename and timestamp so
naturally they differ.

To actually test gzip, do for example:

$ gzip -c test.bin > 1.gz
$ gzip -c test.bin > 2.gz
$ md5sum *gz
aca340cd42ffd3b2c6a25b646637cae5  1.gz
aca340cd42ffd3b2c6a25b646637cae5  2.gz

...or if you want to do it with tar, need to tell it to pass -n to
gzip, for example:

$ tar c test.bin -I "gzip -n" > 1.tar.gz
$ tar c test.bin -I "gzip -n" > 2.tar.gz
$ md5sum *gz
03d30b886f9a2f5219909662586e44b5  1.tar.gz
03d30b886f9a2f5219909662586e44b5  2.tar.gz